182 THE AMERICAN NATURALIST [Vol. XLV 



tion on which Ancylus occurs, is sometimes left uncov- 

 ered when by dry weather the water becomes low. In 

 this part of the lagoon three Gundlachia were found. 

 In general the water of the lagoon is deep and constant, 

 but owing to the presence of these shallows the hypoth- 

 esis that the formation of a septum in Gundlachia may 

 be due to alternation of wet and dry periods can not be 

 wholly excluded. 



Ancylus occurs in one to three feet of water where 

 Ceratophyllum is abundant. In the deeper water shore 

 there is more Nuphar and less fine vegetation the Ancylus 

 seems to be absent or rare. 



Mr. Allen attempted to domesticate the Thornburg 

 Ancylus, placing many young ones in a 15 X 9-inch jar 

 stocked with Anacharis from the lagoon. Apparently, 

 all soon disappeared, although Lymncea and Amnicola, 

 coincidentally transferred, lived a long time. 



Notes on the Several Jabs used as Aquaria 

 The 15 X 9-inch Jar. — This originally contained a 

 dwarf Nymphaa which died. There was a mixture of 

 peaty and ordinary soil about three inches deep in the 

 bottom of the jar. This was stocked in 1906 with 

 Anacharis and some specimens of Vivipara. The date 

 of the first appearance in it of the ancyloid stage of 

 Gundlachia was not determined. February, 1907, individ- 

 uals were very numerous and, some being taken out to 

 save in the dry state, the septate form was discovered. 

 Mr. Allen had noticed the presence of the ancyloid form 

 some time before. The first date at which Gundlachia 

 had been obtained from the Thornburg lagoon was July 

 15, 1906, but Mr. Allen doubts if the copious swarm of 

 ancyloid individuals of Gundlachia could have originated 

 in the jar so quickly from individuals accidentally put 

 in at that time. Some of the vegetation in the jar had 

 been received from elsewhere in Ohio, and some from 

 another state. The ancyloid stage of the Gundlachia 

 can not be distinguished from the associated Ancylus by 



